When I clicked the "edit" link I did not see the pending edit but was presented with the normal edit UI. When I tried to commit the change I got the "You seem to be improving a post but haven't made a change" message.

I tried several times and never saw the pending edit.

At this point (still unaware of the pending edit) I came over to meta to see if anybody else had reported this and found a post which clued me in.

I went back to SO and tried to edit again, and still got the same behavior. It was only when I finally refreshed the page that I saw the edit(0) notation.

In case anybody's interested, here's my analysis:

I started to edit at nearly the same time as the other user; both of us saw the normal edit UI.

The other user committed first

When I tried to commit, the validation logic assumed I came from the "improve an edit" UI and gave me what it thought was an appropriate message. When I dismissed the error box I saw the original post with the typo.

I know this is a low-probability race condition (well, maybe not THAT low) so I thought I'd report it.

Tagging as a bug, but I understand if this isn't considered important enough to fix.

I understand WHY this happened, my point is that the validation code could be smarter about where I came from and not assume I was on the "improve an edit" screen when generating the error message.
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Ex UmbrisApr 18 '12 at 5:26